Ceramic coated bushings and allied products



J. J. MELE 3,048,061

CERAMIC COATED BUSHINGS AND ALLIED PRODUCTS Aug. 7, 1962 Original FiledDeo. l5, 1958 fa 35 i2 INVENTOR.

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y arrasar latented Aug. 7, 1952 3,048,061 CERAMKC CATED lilUSGS ANDALLIED PRODUCTS Joseph J. Mele, North Bellmore, NSY., assigner, by mesne3 Claims. (Qi. 'T- 62) This application is a division of `applicationSerial No. 783,528, filed December l5, 1958.

The invention relates to drill bushings and has special reference to thepreparation of drill bushings and related items coated with ceramicmaterial in order to improve the performance of drill jigs and drillblocks when assembled with drill bushings.

Since the advent of types of drill bushings which are set `in positionin drill blocks by use of plastic, there has been a very markedimprovement in the accuracy of drill blocks and in the ease with whichdrill blocks for use on a great variety of work pieces can be made, Alimiting element, however, in the employment of drill bushings set in `apotting resin has been the inability of the resin to withstandrelatively high temperatures which often occur in regular manufacturingprocess as, for example, when the drill is carelessly used, when thedrill bit is not properly sharpened, and also when materials are workedupon wherein the character of the metal or other material is one proneto overheat to a degree, either because of the character of thecomposition or the thickness of the materi-al which is to be drilled.Potting plastics, although completely satisfactory at temperatures below300 F., become soft at higher temperatures and permit the bushing whichthey encase to shift out of its precise alignment.

One of the seriously objectionable effect-s of a softening of theplastic lies in the fact that in la drill block, for example, containing`a relatively large number of bushings so set in the plastic, one or afew of the bushings may become overheated and consequently misalignedwithout being noticed by the operator and in consequence as workcontinues to be done many complicated and expensively machined partsbecome rejects.

lt is therefore `among the objects of the invention to provide a drillbushing coated with a heat resistant coating which when assembled bypottingr in a drill block is of such character that heat generated in abushing is prevented to a large degree from reaching the potting plas-Y, tic, thereby to produce a drill block capable of being used underadverse conditions for a particularly long run of operating hours.

Another object of the invention is to provide a new and improved ceramiccoated drill bushing wherein the coating is highly heat resistant and isapplied to the exterior surface of the bushing in such fashion that itadheres uniformly `and strongly to the surface of the bushing andmoreover presents an exterior surface on the ceramic which is of asufficiently roughened character and texture to improve the performanceof the drill bushing when set in a drill block by means of a pottingresin.

Still another object of the invention is to provide a new and improveddrill block or drill jig wherein the bushing is highly resistant todetrimental effects of high temperatures by use of a multiple layerconstruction wherein `a ceramic material surrounds and adheres tothedrill bushing and a potting resin lls the remaining space between theceramic material and the surrounding wall of a cavity or aperture in thedrill block.

Also included among the objects of the invention is to produce a new andimproved ceramic coated drill bushing and drill block made therefromwhich has an especially long life, wherein failures are reduced to arelative minimum, which is productive of a relatively minimum degree ofwear on drills used therewith and which furthermore substantiallyminimizes down time of machines and the amount of reworking of partsmade thereby.

With these and other objects in View, the invention consists in theconstruction, arrangement and combination of the various parts. of thedevice, whereby the objects contemplated are attained, as hereinafterset forth, pointed out in the appended claims and illustrated in theaccompanying drawings.

ln the drawings:

FIGURE l is a schematic plan View of an .apparatus by means of whichdrill bushings are coated with a ceramic coating.

FIGURE 2 is a cross-sectional view taken on the line 2--2 of FIGURE 1.

FlGURE 3 is a perspective View partially broken away showing one form of`a drill bushing and appropriate ceramic coating.

FIGURE 4 is a longitudinal sectional view 4of a eramic coated drillbushing afhxed in a drill block by use of a potting material.

In an embodiment of the invention chosen for the purpose of illustrationthere is shown in FIGURE 3 a ceramic coated drill bushing 1li whichconsists of a metal bushing 11 Iand a layer of ceramic coating material12. Extending through the bushing is a drill passage 13 and on theexterior of the bushing is a pattern 14 of configurations which in thepresent example comprise a series of diamond-like projections. It willbe appreciated, however, that virtually any desired pattern may beemployed which is productive of -a sufficient amount of projections and`depressions to provide a suitable grip when the resulting product is tobe ultimately used. When employing the pattern 14 shown afterapplication of the coating material, there will be a facsimile 15 of thepattern on the exterior of the coating material wherein the projectionsand depressions are reproduced but with more rounded vedges and corners.

In order to produce the coated bushing above made reference to, specialprocessing needs to be followed. After the drill bushing has initiallybeen formed in the customary accepted fashion, it must be thoroughlycleaned and degreased. Degreasing may be followed by application of ablack oxide finish or by Sandblasting in order to prepare an adequatesurface to which the ceramic coating will ultimately adhere in asatisfactory fashion. The treatment, moreover, must be entirely connedto the vexterior surface so `as to in no way afect the character of thesurface of the drill passage 13 through the bushing.

After these operations have been completed, a series of the bushings. 11are placed upon a rod 16. The rod is one mounted in appropriate bearingfixtures 17, one of which is illustrated by way of example in FIGURE l.A sprocket 18 is non-rotatably fixed to `an end 19 of the rod inposition to be engaged by a chain Ztl driven from an appropriateconventional power source in order to rotate the rod 16 at a desiredrate of rotation.

'For applying the coating, use is made of a flame spray nozzle 2.1 ofaccepted design mounted upon a carriage Z2. which travels upon a chain23 which in turn travels over sprockets 24 driven by shafts 25, one ofwhich is illustrated by way of example in FiGURE l. Inasmuch as thedrive mechanism is of any substantially conventional design, it will beunderstood that the drive should be one adapted to move the nozzle Z1 toand fro in a horizontal direction from one end to the other of the rod16, whereby to reach all of the bushings 11 in turn which are mountedthereon.

The nozzle 21 is of a known `design commercially available supplied byconduits 26, 27 and 28 adapted to carry into the nozzle respectivelyoxygen, acetylene and air in appropriately regulated quantities wherebyto provide the means of melting and driving material from a rod 29 ofceramic material in such fashion that the material emerges in a spray 30from a tip 3l of the nozzle.

The spraying technique commonly known as flame spraying is one adaptedto melt a material such as alumina (A1203) and zirconia (ZTOZ) and otherappropriate ceramic substances, so that the ceramic material iscompletely molten when it emerges as a spray from the nozzle tip,whereby it can be `directed against the previously prepared surface ofthe bushings.

ln addition to properly adjusting the size and form of the spray 30 asit emerges from the nozzle tip so that it will impinge upon the adjacentsurface of the drill bushings, there is provided a deflector 32 whichforms a progressively diminishing deilector passage 33 thereinthroughout the entire length of the rod lr6. lt will be apparent that asthe nozzle 21 travels in a reciprocating direction from one end to theother of the rod le and the deector 32 and reverses direction along thesame path of travel as frequently as needed, the molten ceramic materialwill be passed through a deilector passage and emerge close to theadjacent surface of the drill bushings where it will impinge upon andadhere to the surface `of the bushings.

In view of the necessity of raising the ceramic material to `atemperature sucient to melt it which may be well in excess of 3000" F.,it will be understood that the temperature of the bushing material whichis usually a steel alloy must be maintained far below that temperaturein order that the alloy will not be damaged during the sprayingoperation. To accomplish this the rod 16 is rotated continuously so thatthere is substantial movement of the surfaces of the bushings while thespray is impinging upon them. The rate of movement should be sufcientlyrapid so that there is no dwell long enough to permit heat to build up.

Because, however, of the exceptionally high temperature differentialbetween that of the molten spray and the temperature above which thebushing must not be heated, additional means is provided in order toprevent accumulation of heat at any one point, especially where drillbushings of relatively small size and thin walls are to be coated.Accordingly, the nozzle 21 is kept in constant motion to and frothroughout the entire accumulated loading of the bushings lil on the rodle while the rod is turning. ln this manner the coating is graduallybuilt up on the surface of the drill bushings to the desired thicknessin a gradual fashion and at a temperature which will not be damaging tothe material of the bushings.

To further insure against the concentration of heat at a damaging level,there is provided an air cooling system consisting of columns 35, one ofwhich is illustrated in FIGURE 2 mounted upon a suitable support 36, atthe top of which is a pipe 37 connected thereto, the pipe 37 extendingthroughout the entire length of the rod 16. Apertures 38 spaced one fromanother throughout the length of the pipe are directed toward thebushings on the rod lr6 so that they are bathed in a mass of cooling airor other appropriate gas throughout the entire coating operation.

It will be understood from the foregoing description that the bushingsmust be slid freely upon the rod )le so that they can be readily placedthereon and moved therefrom after coating but must have `a sufficientlysnug t upon the rod to insure the bushings being constantly anduniformly rotated during the spraying operation as the rod is rotated.The amount of build up of ceramic material on the surface can becontrolled by the length of time of the coating operation and, wheretemperature permits, by the speed of rotation of the rod 16 and the rateof travel of the nozzle 211, within limits set by the necessary amountof cooling. Effective thicknesses of the coating material have beenfound to range somewhat Widely between approximately .010 inch andzO-SOinch, depending to a large degree upon the size of the bushing which iscoated and the pattern of configuration on the exterior of the bushing.In the interest of good performance it is desirable that the coating beno thicker than that necessary to provide a sufficient obstruction tothe flow of heat from Vthe bushing to the exterior of the coating,whereby the amount of material forming the coating can be kept to aminimum and the outside diameter of the coated bushing can also be keptto a minimum.

When the coated bushing is to be used, it is potted in a drill block i0of conventional kind by use of a potting resin 4l. The usual manner ofsetting drill bushings in a drill block like the block d0 is to drill ahole 42 in the block approximately one-quarter of an inch greater indiameter than the outside diameter of the coated bushing, after whichthe bushing is placed within the hole where it is held by a properlylocated pin, not shown, Whereafter the potting resin al is poured intothe remaining annular space between the. exterior surface of the coateddrill bushing and the wall of the hole 42. A sufflcient length of timeis allowed for the potting material to thoroughly set.

The coated drill bushing is securely held by the potting resinespecially where the exterior surface of the coating is of a texture andform such as that described herein whereby the bushing once assembledwill not easily be pushed out of its setting under the adverseconditions provided against by the apparatus herein described.

In use even though temperatures generated in the drill bushing by dulldrill bits and friction may reach from 700 F. to 900 F. and on someoccasions higher, the ceramic coating will act as a darn whereby toprevent passage of heat at these high temperatures to the potting resinand hence the resin will not soften and will continue to retain thecoated drill bushing in its proper position without deviation forexceptionally long periods of use.

It will further be understood that by providing effectively ceramiccoated bushings wherein the ceramic coating is suitably bonded to theentire exterior roughened surface of the drill bushing, the drill blockformed with the coated bushings can make usel of already standardizedprocedures and the highly eicient coated bushing and assembly thereofdescribed in the foregoing disclosure can be introduced into alreadywell-known procedures making available to shops and establishmentsalready using potted drill bushing techniques the extremely long life ofthe coated drill bushing without substantial change or deviation fromother established techniques.

Moreover, by providing a relatively thin ceramic coating upon the drillbushing, the outside diameter of the coated bushing is only slightlygreater than the outside diameter of the bushing itself and hence thediameter of the holes 4t2 can be kept small and permit bushings to belocated close together in a drill block where close set holes arenecessary.

While I have herein shown and described my invention in what l haveconceived to be the. most practical and preferred embodiment, it isrecognized that departures may be made therefrom within the scope of myinvention, which is not to be limited to the details disclosed hereinbut is to be accorded the full scope of the claims so as to embrace anyand all equivalent products.

Having described my invention, what I claim as new rand .desire tosecure by Letters Patent is:

l. A drill bushing comprising an inside generally cylindrical metalbushing having a drill passage therethrough and opposed circular endsurfaces dening the end openings of the drill passage, said metalbushing having a circumferentially continuous side wall extending to andbetween said end surfaces and having a pattern of configurations on theexterior surface of said side wall, and a coating of ceramic materialcompletely enveloping said ex- 'Fannie aoaaoei terior side surface, saidcoating being flame sprayed on said exterior surface and having on theoutside area of the coating a modified replica of the exterior surfaceof the .metal bushing wherein conligurations are rounded to a greaterdegree than on said exterior surface and said end surfaces beinguncoated.

2. A drill jig comprising a drill block having holes therein at drillinglocations, a drill bushing having a drill passage therethrough, acoating of ceramic material completely enveloping the exterior sidesurface of the bushing, said coating being flame sprayed on the surface,and a potting plastic material iilling the space between said outsidearea and the inside surface of holes in the block and adhesively bondedthereto whereby to set the bushing in the block.

3. A drill jig comprising a drill block having holes therein at drillinglocations, a drill bushing having a drill passage therethrough, apattern of configurations on the exterior surface of the bushing havinga roughened texture, a coating of ceramic material completely envelopingsaid exterior surface, said coating being iiame sprayed on the surfaceand having on the outside area of the coating a modiiied replica of theexterior surface of the bushing wherein congurations are rounded to agreater degree than on said exterior surface, and a potting syntheticplastic material lling the space between said outside area and theinside surface of holes in the block and adhesively bonded theretowhereby to set the bushing in the block.

References Cited in the le of this patent UNITED STATES PATENTS

1. A DRILL BUSHING COMPRISING AN INSIDE GENERALLY CYLINDRICAL METALBUSHING HAVING A DRILL PASSAGE THERETHROUGH AND OPPOSED CIRCULAR ENDSURFACES DEFINING THE END OPENINGS OF THE DRILL PASSAGE, SAID METALBUSHING HAVING A CIRCUMFERENTIALLY CONTINUOUS SIDE WALL EXTENDING TO ANDBETWEEN SAID END SURFACES AND HAVING A PATTERN OF CONFIGURATIONS ON THEEXTERIOR SURFACE OF SAID SIDE WALL, AND A COATING OF CERAMIC MATERIALCOMPLETELY ENVELOPING SAID EXTERIOR SIDE SURFACE, SAID COATING BEINGFLAME SPRAYED ON SAID EXTERIOR SURFACE, AND HAVING ON THE OUTSIDE AREAOF THE COATING A MODIFIED REPLICA OF THE EXTERIOR SURFACE OF